A098891 - OEIS

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A098891

Define the n-omino graph to be the graph whose vertices are each of the n-ominoes, two of which are joined by an edge if one can be obtained from the other by cutting out one of the latter's component squares (thus obtaining an (n-1)-omino for most cases) and gluing it elsewhere. The sequence counts the edges in these graphs.

0, 0, 1, 8, 47, 266, 1339, 6544, 29837, 133495, 585002, 2542563, 10959656

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,4

COMMENTS

In some cases the act of removing a component square (temporarily) disconnects the polyomino before the component is reattached elsewhere. - Sean A. Irvine, Apr 13 2020

See A367435 for the case where the cells remaining after detaching the square to be moved must be a connected polyomino. - Pontus von Brömssen, Nov 18 2023

LINKS

Table of n, a(n) for n=1..13.

Freddy Barrera, Picture for a(5), 2020.

Freddy Barrera, Picture for a(6), 2020.

Sean A. Irvine, Java program (github)

FUNG Cheok Yin, Tetrominoes

FUNG Cheok Yin, Maxima code for n = 4 and n = 5, Apr 13 2020

CROSSREFS

Half the row sums of A367126.

Cf. A367435.

Sequence in context: A296631 A255720 A014524 * A054488 A034349 A296797

Adjacent sequences: A098888 A098889 A098890 * A098892 A098893 A098894